The following code is intended to retrieve a file via FTP. However, I'm getting an error with it.

serverPath = "ftp://x.x.x.x/tmp/myfile.txt";

FtpWebRequest request = (FtpWebRequest)WebRequest.Create(serverPath);

request.KeepAlive = true;
request.UsePassive = true;
request.UseBinary = true;

request.Method = WebRequestMethods.Ftp.DownloadFile;                
request.Credentials = new NetworkCredential(username, password);

// Read the file from the server & write to destination                
using (FtpWebResponse response = (FtpWebResponse)request.GetResponse()) // Error here
using (Stream responseStream = response.GetResponseStream())
using (StreamReader reader = new StreamReader(responseStream))            
using (StreamWriter destination = new StreamWriter(destinationFile))
{
    destination.Write(reader.ReadToEnd());
    destination.Flush();
}

The error is:

The remote server returned an error: (550) File unavailable (e.g., file not found, no access)

The file definately does exist on the remote machine and I am able to perform this ftp manually (i.e. I have permissions). Can anyone tell me why I might be getting this error?